


A beasty monster

by heloflor02



Category: Undertale (Video Game)
Genre: F/M, Gasterblaster AU, Specieswap AU
Language: English
Status: Completed
Published: 2018-02-28
Updated: 2018-02-28
Packaged: 2019-03-25 04:03:19
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,000
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13826076
Author URL: https://archiveofourown.org/users/heloflor02/pseuds/heloflor02
Summary: After almost a month since monsters swapped species for unknown reasons, two years after Frisk freed them all, Toriel discovers a certain power of skeletons monsters that has always been hidden to everyone.





	A beasty monster

**Author's Note:**

> Just a random thing 'cause of the Soriel discord who got into SpeciesSwap for a short while and once mentioned GB Toriel, which inspired me.

Toriel woke up by the sound of her alarm clock. When she stopped it, she stayed surprised for a second, seeing her hand being only bones; but she quickly remembered what happened. For almost a month now, all monsters “swapped” their species, mostly between people who care a lot about each other.

She started to sit to get up, only to feel her short, now-goat husband clinging to her. She smiled, gently petting his head before slowly getting out of his grip. However, as she sat, she felt some pain in her skull, making her stop moving for a moment. During that time, as usual, she could hear Sans' hand slowly moving where she previously was, looking for her, before it stopped and the goat monster opened his eyes, waking up.

 

“Hey Tori.”, he murmured.

 

“Hello my dear. Did you have a good sleep ?”

 

“heh. Yep.”

 

“Good.”, Toriel suddenly felt pain again and put a hand on her skull.

 

“Something's wrong ?”, Sans asked, lying down next to her and encircling the Boss monster's body with his arms.

 

“I am fine.”, she answered. “It is just a little bug.”

 

“You sure ? I never saw you sick before.”

 

“This is surely because goat Boss monsters are not getting much sick. But do not worry, I have been sick in the past, I can easily handle it.”

 

“...Just remember that skeletons are weaker because we-... _they_ don't really have the organic material to help.”

 

“I know; and I will be fine.”, she bent down to make her skull touch his head as a way to show affection, according to what Sans told her about skeletons, before she stood to start the day.

 

 

 

 

If Toriel claimed that she would be fine, she had to admit that she was feeling terrible, her head still hurting a lot; and she started to get vertigo. Once dressed, she asked Sans to wake up the children and, when she went to the kitchen, she felt relieved to see Papyrus already cooking and left herself fall on a chair.

 

“ARE YOU ALRIGHT ?”, the not-so-tall goat asked.

 

“I just have a little illness, nothing too terrible.”, she answered. “But, um; do you mind if I do not help you with breakfast ?”

 

“OF COURSE NOT ! IF YOU'RE SICK, YOUR RECOVERY IS THE MOST IMPORTANT; AND I THINK I'M GETTING A GOOD GRIP ON FIRE MAGIC NOW !”, he proudly made a fireball as he said that before getting back to his work.

 

Toriel smiled, watching as he continued. After some time, the children arrived.

 

“Hi mom !”, a red-eyes child cheerfully said as they went to the table. “Hi uncle Papyrus !”

 

Toriel felt a bit weird out to see them acting like that. After all, even if she was aware that, because of them living with monsters which made them have some magic in them, Frisk and Chara swapped bodies the same moment as monsters swapped species; she was too used to how they were before that event and always took a second to remember who she was talking to.

The two other came in and made their greetings, Chara having their usual expression, or at least what seemed like their usual expression with Frisk's face; while Asriel was looking kinda down, which saddened Toriel. Her son didn't take it well to become a skeleton and seemed like he could never get used to it. Though, today, he seemed even more down than usual.

Shortly after, Sans came and sat to face his wife.

 

“Are you ok ?”, he murmured.

 

“I am fine.”, she replied with some annoyance and maybe too loudly.

 

“Is there something wrong with mom ?”, Frisk asked, bringing the other children's attention.

 

“Just a little illness, no need to worry.”, she answered.

 

“Is that because you're a skeleton now ?”, Chara asked, making a quick glare at Sans.

 

“Everything is terrible as a skeleton...”, Asriel murmured, his face resting on the table.

 

“Hey, come on kid, light up.”, Sans said. “At least you don't have to deal with how to get used to...that !”, he opened his arms as a way to show his goat body. “Now that I'm like that I have ta use bathrooms, brush all this fur, watch out for my horns when I try to wear anything and I can't even eat random stuff like ketchup anymore 'cause I gotta “take care of my health”. And I can't even teleport anymore !”

 

“AT LEAST YOU'LL LEARN HOW NOT TO BE LAZY AND APPRECIATE MORE TO BE OUTSIDE WHEN YOU GO OUT !”, Papyrus said as he started to serve everyone.

 

“Yeah...but anyways.”, Sans turned back to face Toriel who was hesitant about eating, considering how she was feeling. “Are you sure you can handle going to school and teaching like that ? Maybe you should take the day off ?”

 

“...I suppose.”, she sighed. “But please Sans, I know you planned on working with Alphys today and I do not want you to cancel it just because if my state.”

 

“Alright”, he firmly answered, though he was still looking worried.

 

“Now, about the children...”, Toriel started, looking at the trio.

 

“I WILL BRING THEM TO SCHOOL !”, Papyrus said before any question was made. “AFTER ALL, I PLANNED ON DOING SOME GROCERIES. AND IF IT CAN REASSURE MY BONEHEAD OF A BROTHER, I WILL TRY TO COME BACK HOME QUICK.”

 

“Bro, I'm not a bonehead anymore here.”, Sans said, pointing his head.

 

“BUT GOATS HAVE SKELETONS UNDER ALL THAT FUR !”, the younger brother replied as if this fact was something not much knew, something that he wasn't aware of himself some months earlier.

 

“Heh, you _goat_ me there.”

 

“SANS !”, on the other side of the table, Asriel's groan could also be heard, making Chara snort.

 

“It's just a joke Paps. No need to be so maaad about it.”

 

“Indeed. There is no reason to _rattle your bones_ over that one.”, Toriel said, which made Sans laugh.

 

“THAT'S IT ! I'M OUT !”, Papyrus got up, his plate in hand. “CHILDREN, COME TO THE GARAGE WHEN IT'S TIME TO GO. I WILL BE WAITING FOR YOU THERE.”

 

“Alright then.”, Chara replied while Frisk had an amused face and Asriel had his hands on his skull.

 

“I can't even cover my ears with this body...”, he quietly grumbled.

 

“Come on Azzy !”, Chara started. “After all-”

 

“DON'T !”, Asriel screamed.

 

Chara bursted into laughing, followed by Sans while both Frisk and Toriel smiled, amused. Though, Toriel was kinda worried.

 

_Why is Asriel so...tense today ? He never got so mad because of a pun before..._

 

She shook her head, deciding that it must be because of all the time spent as a skeleton and that, if he wasn't feeling well at school, his father would be around to help him.

Quickly after, the other two calmed down and the family went back to their morning routine.

 

 

 

 

One hour had passed; Toriel was lying down on the couch, feeling even worse than earlier.

 

_Is it really a normal sickness ?...I hope it is._

 

Suddenly, she started to feel strange. She started to shake, her bones rattling as a nausea took her. She put a hand on her teeth and quickly noticed that her hand was changing, her fingers getting bigger. Her headache became worse, making her fall from the couch as her body changed faster. It became bigger, ripping her clothes off, while her hands turned into strong paws, her head took what felt like an animal form, and she could feel a tail growing.

After some time, her pain stopped and she realized that she wasn't feeling much sick anymore. Though, for a time, she stayed still, confused, afraid of what just happened to her. Finally, she tried to stand then looked at herself and felt even more confused.

She had become some kind of giant skeleton beast. Looking around, she saw that all her clothes were destroyed, aside from her wedding ring which was still on her. She sat down.

 

_What just happened ? Why did it happened ?! Will I...stay like this forever ?_

 

She sighed, which sounded more like a growl. Surprised, she tried to talk, only to end up doing some dog noises.

 

_Of course..._ she mentally grumbled before lying down where she was, trying to get some rest considering how exhausted this transformation made her feel.

After some time, she heard the door opening.

 

“I HAVE RETURNED !”, Papyrus declared, his hands full of groceries.

 

Toriel felt panicked. Never she saw one of the brothers turning into a different creature and she was scared that they wouldn't recognize her and think that she was a beast who hurt the former Queen.

 

“HOW ARE YOU FEELING TOR-...OH.”, he started at her, not looking very surprised, which didn't ease her.

 

Toriel started to walk backwards, whining a little.

 

“OH, NO; D-DON'T WORRY.”, Papyrus quickly put his bag down and slowly walked to her. “IT'S OKAY, I KNOW WHAT HAPPENED TO YOU, DON'T BE AFRAID.”

 

Toriel kept moving, unable in her panic to understand what he was saying, until she ended up with her back against a wall. She closed her eyes as the other one was approaching, not wishing to hurt him in her panic. Suddenly, she felt his hand on her head, gently rubbing her muzzle.

 

“THERE, THERE.”, he murmured. “EVERYTHING IS ALRIGHT. YOU WON'T GET HURT.”

 

She started to calm down, understanding that this hand won't hurt. Though, she felt surprised of how the goat was talking to her.

 

_It is the same tone as when he talks to Sans after one of his nightmares...has Sans ever transformed into a beast ?_

 

After a short time, he put his hand away, looking a bit stressed.

 

“SO UH... I GUESS YOU WANT AN EXPLANATION ?”, he looked as if he did something wrong, which made Toriel quickly understand that he was aware of that form for a long time now. She nodded. “WELL, REMEMBER HOW ME AND SANS...GO TO SEE SOME FRIENDS ONCE A MONTH FOR TWO DAYS ?”, Toriel inclined her head as she was listening. “WELL... IT WASN'T REALLY THE CASE. EACH TIME, WE WENT TO AN ISOLATED PLACE IN THE CLOSEST WOODS AND WE...WAITED UNTIL OUR TRANSFORMATION WAS OVER.”

 

_So this happened to them. And they hid it all this time ?!_

 

She looked at the goat monster with a severe look.

 

“H-HEY, PLEASE DON'T BE MAD ! WE JUST...WHEN WE WERE STILL LIVING IN SNOWDIN, WE GO USED TO HIDE FROM OTHERS; AND WHEN WE WENT TO THE SURFACE AND STARTED TO LIVE WITH YOU AND FRISK...I TRIED TO TALK SANS OUT ABOUT IT, TELLING HIM THAT HE HAD TO BE HONEST WITH YOU BUT...”, Papyrus sighed. “YOU KNOW HIM...”

 

Toriel looked down at her paws, feeling sadness and anger to know that her husband hid her such a thing.

 

“SPEAKING OF SANS...” Papyrus suddenly continued. “I SHOULD PROBABLY TELL HIM THAT YOU TRANSFORMED.”

 

The goat monster pulled out his phone while Toriel went back to lie down on the carpet in front of the couch. Even though she didn't like eavesdropping, the skeleton decided to listen to the conversation.

 

“HELLO BROTHER ! WELL, I WANTED TO TELL YOU; IT'S ABOUT TORIEL. NO NO, SHE'S NOT GETTING WORSE. SHE JUST...TURNED INTO A BLASTER ?”, he had a weak smile as he said that.

 

“wait what ?!”, even Toriel could hear Sans' scream of surprise, followed by what sounded like a million questions.

 

“YES SHE'S FINE !”, Papyrus answered. “THOUGH, I NOTICED THAT SHE SEEMS BETTER THAN EALIER SO HER ILLNESS WAS PROBABLY A REACTION TO THE TRANSFORMATION. I DON'T KNOW, WHEN I CAME SHE ALREADY WAS A BLASTER.”

 

_A Blaster ?_ She thought, hearing that the word was used twice to describe her new state.  _I am a “Blaster” ?_

 

“NO, SHE SEEMS FINE; AND WITH THE ILLNESS THERE'S NO WAY HER TRANSFORMATION WAS AS PAINFUL AS YOURS.”

 

_Painful ? Sans' transformation hurt him that much ? And he never told me about it ?!_

 

Toriel raised her head to face Papyrus who noticed her movement and offered her an understanding look while pointing his phone to indicate that, for now, he had a brother to reassure.

 

“WAIT SANS, DIDN'T SHE TELL YOU NOT T- I SUPPOSE BUT SHE'LL BE MAD.”, Papyrus took a second to sigh. “IF YOU SAY SO. BUT DON'T BLAME ME IF SHE GETS MAD ! LATER.”, Papyrus hung up and turned to Toriel. “SANS SAID HE WOULD COME BACK HOME; THAT ALPHYS CAN FINISH THEIR STUFF ALONE.”

 

Toriel nodded, getting back in her lying position. _Once back, he will have some explanation to do !_

 

She looked as Papyrus moved to the groceries and started to get it in the kitchen. She quickly got up, wishing to help but realized a problem : her transformation made her too big to pass the kitchen's doorway. She grumbled, getting back to the the living-room. She could hear Papyrus whispering a “SORRY” when he came back to take the last bags.

After some time, while Papyrus was arranging the groceries, the phone rang. The goat quickly came and answered, Toriel listening as she sat next to him.

 

“HELLO ? NO, I'M HIS BROTHER; I'M SORRY BUT HE'S NOT HOME YET. NO,”, he looked at the skeleton blaster for a second “SHE CAN'T ANSWER EITHER; SHE'S...STILL SICK. OF COURSE !...OH. I, I WILL TAKE CARE OF THAT; DON'T WORRY HUMAN, I'M COMING !”, after that, he hung up, sighing as he turned to Toriel. “IT WAS THE SCHOOL; ASGORE AND ASRIEL TURNED INTO BLASTERS TOO. THIS WILL BE A LONG DAY...”

 

 

 

 

Toriel was walking back and forth in the room, feeling a bit worried for Asriel but mostly not wanting to spend the entire day sleeping all because of her size. _I should have asked Papyrus to open the long door to the garden..._ The goat monster was out after having texted his brother, who apparently blamed his new form even more for not having teleportation powers.

Suddenly, the door busted open as the short goat arrived.

 

“Tori ! Are you alright ?!”, Toriel rolled her eyes, amused, while her husband came closer to her, putting his hands on her cheeks. “Paps told me everything. Are you feeling alright ?”, Toriel answered with a nod. “heh, good. Look, I...I'm sorry I didn't tell you about this before. I just...never thought you'd have to deal with it.”, Toriel looked at him with an angry look, hoping he was aware that she heard about how terrible the transformation was for him. “Don't look at me like that; I was just trying to protect you from the idea of me and my bro becoming beasts for no reason !”, her look became angrier. Sans sighed, putting his head against hers. “I'm really sorry Tori. I was so used to hide from others, it made me scared of how everyone...how _you_ would react to it. I knew that I had to tell you one day or another but...heh, you know me...”

 

The two stayed in the same position for a time, Toriel letting Sans calm down. Then, Sans pulled back, meeting her gaze again.

 

“So uh...I guess you wanna chill down and rest ? I mean, you're probably a bit shaken by the transformation, right ?”

 

Toriel shook her head at that and approached the big glass door leading to the garden, sitting in front of it.

 

“You wanna go outside ? Heh, yeah, ya probably spend the entire morning resting.”

 

He opened the door to her and she ran outside, taking a deep breath. She stayed surprised for a second when she realized how much her sense of smell was developed. She could smell everything around her. She also quickly noticed that she could hear everything as well. For a moment, she closed her eyes, letting her senses coat her from everything around.

 

“Say Tori.”, Sans' voice shook her out of her state. She turned to him. He was taking a random frisbee that belonged to Frisk. “Wanna play a little ?”

 

She looked, confused, until the short goat threw the frisbee in the air. She suddenly had a strong wish to catch him, feeling playful, and started to run to it.

 

_So this is what dogs feel each time someone bring them such a toy._ She thought as she caught the frisbee mid-air, tail happily swinging. She moved back to Sans, who was looking amazed.

 

“Damn Tori, I didn't know you could jump like that !”, Toriel answered with a smug face and, as Sans tried to take the frisbee, she kept it, taking a playful position, almost like a dog would. “So you wanna play the hard way huh ? Gimme that !”

 

Sans quickly tried to snatch it from her jaw. Toriel kept a good grip on it, forcing quite a lot, even though she knew that she was way stronger than him. Suddenly, after a last effort, Sans let it go, making him fall head-first on the group while Toriel tried to keep her balance from the sudden lack of resistance. Once she did, she noticed her husband lying down. Worried, she let the toy, running to him and putting her head on him, making a little whine.

 

“M'fine.”, he quietly said as he raised his head and started to slightly pet her. “It's just a little fall. Heh, no bones broken.”

 

She stood back to let him some space to get up.

 

“So.”, he said once back on his legs. “Wanna keep up with the game ?”, he pointed the frisbee.

 

Toriel nodded, promising herself to be more careful with her new strength.

 

 

 

 

After some time, Toriel heard a car coming. Guessing it was Papyrus bringing back her child, she hurried back into the house, followed by a surprised Sans. She sat in front of the door as she saw it getting open.

 

“I'M BACK WITH ASRIEL !”, the goat announced as he entered the house, a little blaster following him.

 

Asriel shyly looked in the house. He quickly noticed his mother and slowly approached her.

 

“Mom ? You transformed too ?”

 

Toriel was surprised to be able to understand him, but a short glance to the two brothers made her see that only her could understand what he son was saying.

 

“I did.”, she answered, gently petting his head with hers. “But do not worry, this is apparently only temporary. It may be over in two days.”

 

“But Papyrus told me that it will happen again next month...”

 

“I suppose...”, she shook her head. “But I am sure we can live with it. And who knows, maybe we will get our goat forms back and will never transform again !” _But I will have to keep an eye on Sans and Papyrus if it happens. I cannot leave them suffer alone again._ “Say.”, she continued. “How is your father doing with his transformation ?”

 

Asriel looked a bit surprised, probably wondering why his mother would ask about Asgore, even though he knew that the two became friends again.

 

“Dad was...really surprised with his transformation. And when he saw the others getting scared of him, he just stood away, though I think he was also looking for me. Good thing it happened during recess; I was so scared, I could have hurt someone in a classroom !”

 

“What happened then ?”, she asked, staying close to Asriel as a way to comfort him with the scare he had.

 

“A teacher tried to talk with dad. He couldn't understand what dad was saying but saw that we were both calm so he asked us to stay in the yard while he would call someone for us. Then Papyrus arrived and told us he would bring us here but dad found a way to say that he wished to go back to his own home. Though, Papyrus quickly went to the gym to ask Undyne to stay with dad to keep an eye on him in case he would get hurt.”

 

“I see. Thank you for telling me all this.”

 

“You're welcome mom.”, the two blasters stayed together for a moment before pulling away.

 

“So, kid.”, Sans started when he saw that the two stopped talking. “How about we go play throw and catch outside ? Heh, it's not like you and your mom can do much activities inside in this form anyways.”

 

Asriel looked at Sans in a hesitant way but his tail was wiggling joyfully and, after a short moment, he started to head to to the door, followed by his mother and step-father.

 

 

 

 

The rest of the morning and the afternoon were rather calm, both Blasters playing with the now-goat brothers in the garden. Though, Toriel started to feel less comfortable being in this form when, at a point, Asriel sneezed, making an enormous beam of light. If it wasn't for the brothers who quickly acted so that her son sneezes in the air, something or even someone could have been greatly damaged.

 

_No wonder Sans and Papyrus went to a forest each time they transformed. We need to be very careful with our magic or we may be dangerous for others..._

 

After that, no other events of magic manifestation happened and everyone was safe when the two human children came home. They seemed a bit surprised to see their mother transformed but looked like they expected it. They also directly asked to play with Asriel but Toriel's expression, helped by Sans who could talk for her, made they understand that they had to do homework first.

The evening was also calm, all children being in Chara and Asriel's shared room, the young blaster being able to go over doors, unlike his mother. For dinner, Papyrus took care of the cooking and, like he did for lunch, he gave the two blasters' food on plates on the ground, which made Toriel wonder of she had to feel offended to be feed like a dog or feel thankful that the goat was trying to make it easier for them to eat.

After one last hour, everyone went to sleep. From the little she could see through doors, Toriel saw that Asriel found a way to sleep on his bed. She sighed, making a grunting noise, before going back to the front of the couch and lay on the carpet in front of it, where her clothes had been removed some hours after her transformation. Suddenly, she felt something on her back. Turning her head, she saw her husband putting a blanket on her before sitting, his back against her body.

 

“What ?”, he asked with a smile. “Ya really thought I would leave you alone all because of that form ?”

 

_You leave me alone for two days each months because of yours._ She thought as she looked at the short goat with an amused smile.

 

“Anyways.”, he continued, closing his eyes. “Good night Tori. And don't worry about that thing you are. Tomorrow, you'll be half transformed, which means that you'll have everything back to normal aside from headshape, tail and some dog behaviors. But none of this should be a problem.”

 

Toriel stared at him for a moment, seeing that his breath started to be slower. She then smiled, putting her head down, closing her eyes and grabbing Sans with her paw to pull him close to her. He made a little sound of surprise before clinging to her, becoming sleepy again.

 

“G'night Tori; I love ya.”, he murmured, at what she responded by a little bark.

 

_Looks like being a Blaster will not be that much trouble, especially if tomorrow I am not a giant beast anymore. But I really need to be careful, this form has way more magic than what I might expect. And..._ she opened an eye to look at the sleeping goat.  _If we ever get our species back...I will have to make sure that they do not run away while transformed. Who knows, maybe these two may have as much fun as Asriel had today, if they accept to look at their transformation as themselves. Maybe...maybe this is the last thing Sans need to be truly happy..._

 

**Author's Note:**

> The “Asriel sneezing into the air to avoid destroying stuff” is from a RP made by others on the Soriel Discord (but the blaster wasn’t Asriel). Also Sans having a very painful transformation and him and Papyrus going to a forest is strongly inspired by Topazshadowwolf's GB stories she made some months ago (go check her stuff, it's amazing !)


End file.
